Manufacture of alkali-metal cyanide



Pat nt d Me; 24, was.

UNITED sra'rns PATENT caries.

anwm mr'r'ascn: Ann momma, or rmnwrosnasnn-on-rrm-nmnn, one

mnmassrenons r namscrrn amma sons-roams, or- Lunwresnarmv- ON-THl-BHIH'E, GM, .5. CORPORATTOH 0F GERIANY.

"minimum or crmrnn Io Drawing.

To all whom it may concern: I

Be it known that we, Anvmc Mmascn and Wm Mionann, citizens or the German Empire, residing at Ludwigshafen on-the-Rhine, Germany, have invented new and useful Im rovements in the Mannfacture of Allr'a '-Metal Cyanide, of which the following is a specification.

This invention relates to the production of-commercially pure alkali metal cyanide from gases containing, hydrogen 0 anide especially such gases as contain by rogen cyanide in mixture with carbon dioxid. Such gases as for instance are obtained by 16 the catalytic reaction between carbon monoxide an ammonia and which generally still contain a. certain amount of unaltered ammonia besides hydrogen cyanide and, carbon dioxid, can be worked up only with diflicnlty 20 with a. view to obtain commercially ure alkali metal cyanide which is not spoil by lar' admixtures of alkali metal carbonates.

have found that gas mixtures containing hydrogen cyanide and carbon dioxid can be worked up to form commercially pure cyanide very simply by introducing the gas mixture into a caustic soda solution which has a'high concentration and may even con-.

thin solid sodium hydroxid and maintaining,

so the temperature below about 40 degrees eentigra e.

carbonate arc formed,'and when the concerttration of the causticlsoda solution is sufficiently high the carbonate will for the v chiefv part bepreoipitated at once. A sodium cyanide vsolution is obtained whichcontaans comparative little sodium carbonate; order'to obtain sodium cyanide a state of purityfas is required for trading, we sat: 40 urate the cyanide solution withammorha either after-removin the sodium carbonate which has been precipitated directly or in y the" presence thereof. B the action'of the ammonia a further precipltation of sodium carbonatetakes place and the solution of Egactically pure cyanide can then referably worked up 1n order-to obtain solid cya'uide by distilling of! the ammonia ,con-

tained therein and evaporating to The process formin the bject of'the present invention is rther eaglained by the following exam le to who however the invention is not 1 Q r The solution is now saturated with Sodium cyanide and v .lvpllfilflm ma Inch 5, 1924. semino. camav.

concentration of cyanide corresponding to a about 450 to 500 grams in each litre to be reached and in case of need, solid sodium hydroxid should be added to the solution. When the solution is saturated with the gases introduced, it consists of a concentrated solution of sodium cyanide with small contents of dissolved sodium carbonate, while by far. the greatest quantity of the sodium carbonate has been precipitated.

ammonia without previously removing the sodium carbonate precipitated and while cooling in case the temperature should rise too much. A further amount of dissolved Seous i sodium carbonate is precipitated thereby and the solution of sodium cyanide willgeneral- 1y only contain a fraction of 1 r cent by weight of sodium carbonate culated on the quantity of dissolved cyanide. The solution and the crystals are then separated by filtration and the ammonia contained in the solution 'isedistilled oif by raising the temperature very slowly, and finally the solution is evaporated to dryness in vacuo at t about 50 degrees centigrade.

Under certainv circumstances, especially, when the 'smixture contains a substantial amount 0 gaseous ammonia and when the temperature during the treatment with caustic soda solution is kept very low, and if a very concentrated solution of cyanide isproduccd, the ammonia supplied y the gas mixture may be sufficient to cause fargoing precipitation of sodium carbonate when the'alkali is neutralized so that a so 4 arate addition of bus-ammonia may entirely" dispe ,..with, and' a cyanide and sometimes also a small amOuntT'of presolution racticallyfree from carbonate is v cipitated solid sodium cyanide, may be purified by adding water or aqueous ammonia in an amount corresponding to about double or triple the weight of the cyanide contained in the carbonate and stirring thoroughly. The solution formed containing cyanide and a. small quantity of sodium carbonate is filtered off and may be added to a fresh batch of sodium cyanide solution to be treated with ammonia. The solid sodium carbonate is again washed with a small quantity of strong aqueous ammonia in order to completely remove the cyanide still present. The washing liquid obtained thereby can also be used in the course of the operations for example for preparing the caustic soda solution.

What we claim is l. The process of manufacturing commercially pure sodium cyanide which consists in introducing a gas mixture containin hydrogen cyanide into highly concentrated caustic soda solution, saturating with gaseous ammonia, removing the salts precipitated thereby, if any, and then evaporating to dryness.

2. The process of manufacturing commercially pure sodium cyanide which consists in introducing a gas mixture containing hydrogen'cyanide and carbon dioxid into highly concentrated caustic soda soluti'on, saturating with aseous ammonia, removing the salts prec1pitated thereby and then evaporating to dryness.

3. The process of. manufacturing commercially pure sodium cyanide which consists in introducing a gas mixture containing hydrogen cyanide, carbon dioxid and ammonia into highly concentrated caustic soda solution,-sat urating with gaseous ammonia, removing the salts precipitated thereby and then evaporating to dryness.

4. The process of manufacturing commercially pure sodium cyanide which consists in introducing a gas mixture containing hydrogen'cyanide, carbon dioxid and ammonia into highly concentrated caustic soda solution while maintaining a tempera ture not exceding 10 degrees centigrade, saturating with gaseous ammonia, removing the salts ,precipitated thereby and then evaporating to dryness.

5. The process of manufacturing coinmercially pure sodium cyanide which consists in introducing a gas mixture containing hydrogen cyanide,carbon dioxid and a substantial amount of ammonia into highly concentrated caustic soda solution until the alkali is combined with hydrogen cyanide and carbon dioxid, separating the solid sodium carbonate formed and evaporating the solution to dryness.

In testimony whereof we have hereunto set our hands.

ALWIN MITTASCH. WILHELM MICHAEL. Witnesses:

VILHELM Sonnvnn, ARTHUR DENONVILLE. 

